The present invention refers to a process for getting yarn or cord made of plastic or textile material that will be used for the outfitting of special fabric, specially artificial grass, fully used in sports facilities such as golf fields, tennis courts, athletic stadiums and others. In the same way, the present invention refers to a specifically developed system for the continuous and efficient fulfillment of the process mentioned, avoiding interruptions and discontinuities in this process with the purpose of improving the process eficiency, thus reducing the manufacturing costs. A third objective of this invention refers to a yarn or cord with circular cross-section produced by the system of the invention and through the application of the process of the invention.
Nowadays, the process used normally to obtain basic cord or yarn for the outfitting of special fabric and specially of artificial grass is discontinuous, which involves the use of a synchronized stage system, that has the following stages:
a) Extrusion/fibrillation of a heat-stable plastic material to get a rectangular cross-section profile, in strip or flat yarn form, by means of an extrusion mould with the appropriate shape to fit the wanted dimensions;
b) winding of the mentioned flat yarn around a drum, the winding speed being fixed by the flat yarn production speed;
c) transportation of the complete bobbin obtained in b) to the machine that will make the next stages;
d) twisting, by means of a twisting machine, of the flat yarn obtained in a) to get a helicoidal cord suitable for the following outfitting of the special fabric, particularly the artificial grass;
e) final winding of the yarn obtained in the twisting stage, for its sending to the final product outfit plant. This stage can sometimes be included on stage d).
With the purpose of making available a continuous manufacturing process, keeping the same product quality and output productivity, it has been developed a xe2x80x9cnon-twistedxe2x80x9d yarn by means of a spiral-winding (with a convolution of P mms.) with a very fine monofilament made of polyamid or similar plastic material, to the aim of converting the flat yarn coming from the extrusion stage into a circular cross-section yarn.
The system of the invention for getting the said yarn produces the creation of a continuous process, also an object of the present invention, that avoids any interruption and that joins all the process stages in only one facility, thus saving transportation times and waiting times as well as costs.
The process object of the present invention has three stages:
a) Extrusion/fibrillation of a plastic material to get a flexible, rectangular cross-section, profile in stripe or flat yarn form, by means of an extrusion mould with the appropriate shape to fit the wanted dimensions. This stage is the same as the one used in the existing processes;
b) curving of the flat yarn by means of the wrapping around it one or more threads of plastic material, preferably polyamide, thus obtaining a helicoidal configuration of the group formed by the strip and the wrapping thread or threads, the mentioned wrapping being made by means of the turning of one or more synchronized bobbins around the flat yarn that comes out directly from the extrusion, thus obtaining a circular cross-section cord for the further outfitting of the basic fabric for the manufacturing of the special fabric and especially the artificial grass; this curving-wrapping operation differs substantially from the twisting applied in the existing processes because the cord is formed by the curving of the strip or flat yarn coming from the extrusion and by helicoidal wrapping of the said strip or flat yarn with thread or threads of plastic material, preferably polyamide.
c) Final winding of the yarn or cord obtained in the b) stage for its sending to the final product outfitting plant. This winding stage is the same as the one used in the existing processes.
As can easily be understood from the analysis of the improved process of the invention, it has been possible to eliminate the b) and c) stages from the existing processes. The stage b) of the process of the invention is made by the system of the invention in a synchronized way with the extrusion stage a).
The system of the invention has two sections, the first one consisting of an extrusion device to obtain, from a thermoplastic material piece, a rectangular profile in flat strip form, and the second section that is formed by a tractor/stretcher or pulling device, the pulling speed of which is higher than the feed rate of the extrusion device, and also by a winding device comprising one or more drums that turn around the strip, winding some threads, preferably of polyamide, to get a helicoidal configuration of the final product formed by said strip wrapped by the thread or threads supplied by the mentioned drum or drums. The pulling device and the winding device work in an independent but synchronized way in relation to the output speed of the extrusion device, with the objective of avoiding possible errors that could affect the performance of the system and also the final product quality. This synchronization is reached by any of the synchronization methods known in the present state of the art.